1966 273 Commando - Thoughts

I'm not at all familiar with 273 motors, but "Heads 1.88 Intake and 1.60 exhaust" sound like 360 LA heads to me. Wouldn't the 273 require smaller combustion chambers? I'd verify what compression ratio you're actually going to get by getting the casting number for a Cc estimate against the piston compression numbers. Does seem like a lot for basically a fresh motor with a cam and aluminum intake. Just my .02 worth.